1. Field of the Invention
The present invention relates to an apparatus for producing a stitched-bonded pile surface structure.
2. Description of Prior Art
Carpets or velour pile structures formed by tufting machines are well-known. Tufted structures contain tufts in the form of uncut or cut loops inserted into a "primary" backing. A portion of the pile yarn remains on the back face of the backing. The pre-formed tufted backing is then stabilized by applying a relatively heavy layer of adhesive binder material (usually a latex-based material) and, in most cases, a "secondary" backing to the back of the structure. In some cases a layer of thermoplastic material is introduced between the primary and secondary backings to replace the adhesive binder material.
One limitation of these products is that they require relatively heavy primary backings that can hold the tufts securely until the adhesive binder material and secondary backing are applied. A second limitation is that the adhesive binder material and secondary backing add substantial weight. A third limitation is the considerable portion of the tufting yarn is placed under the primary backing, between the primary and secondary backings. This construction leaves the face of the primary backing exposed between tuft-penetration points, requiring a relatively dense pattern of loops or cut-tufts. Furthermore, "tuft-bind," or the force required to pull cut tufts or to unravel uncut loop tufts, is limited, unless a large weight of binder material is used to penetrate the backings and the pile yarn located between the two backings. EQU --o--0--o--
Flat stitch-bonded structures are also known in the prior art. FIG. 1A is a stylized perspective view of a typical apparatus generally indicated by the reference character 10 for forming a flat, stitch-bonded structure 12 having "laid-in" yarn inlay elements 54 overstitched with a stitching thread. FIGS. 1B and 1C illustrate stylized front and side elevational views of the stitch-bonded structure 12 so produced. It should be noted that in FIGS. 1A through 1C, for purposes of illustration, the yarn 48Y used to form the yarn inlays 54 is shown as being a relatively heavy and bulky yarn of the type typically used to form carpet pile, while the thread 48T (shown in dashed lines in FIG. 1A) used to form the chain stitches 56 is of significantly finer denier.
Each yarn inlay 54 in each of the plural rows of inlays is attached at spaced points to a first, top, surface 14S of a planar backing 14 by the underlap portions 56U of the chain stitches 56. The stitches 56 are linearly interlocked with themselves by overlap portions 56L (FIG. 1B) formed over the second, bottom, surface 14B of the backing 14. A representative stitching apparatus similar in structure and operation to that described herein is manufactured and sold under the Trademark "Malimo" by Karl Mayer Textilmaschinenfabrik GmbH, Obertshausen, Germany.
The stitching apparatus 10 may include a slotted platen 20 that supports the backing 14 along a generally planar path of travel extending longitudinally through the apparatus 10. The slots in the platen 20 are not visible in FIG. 1A. The longitudinal direction of travel of the backing 14, also termed the "machine direction", is indicated by the reference arrow 24. As used throughout this application the longitudinal direction of travel aligns with the longitudinal (or "warp") direction of a pile surface structure being produced, while the direction transverse to the warp direction is termed the "cross", "transverse" or "weft" direction of the pile surface structure being produced.
It is noted that the path of travel of the backing 14 through the apparatus 10 is arbitrarily shown in FIG. 1A as a horizontal path. The backing 14 is supplied to the platen 20 from a suitable supply roll (not shown in FIG. 1A). In the stitch-bonded structure 12 produced by the apparatus of FIG. 1A the backing 14 typically takes the form of a lightly needled staple "fleece", a lightly bonded card web, or a spunlaced sheet. None of these typical backing materials is dimensionally stable. Accordingly, the main purpose of a stitch-bonding operation is to impart stability to the backing 14 in both its longitudinal and cross directions.
The backing 14 is conveyed incrementally in the machine direction 24 by a suitable propelling arrangement, such as a pull roll (not shown in FIG. 1A). Optionally, a hold-down plate downstream of the needle plane may support the backing against the platen in that region. The hold-down plate is omitted from FIG. 1A for clarity of illustration.
At the inlet edge of the platen is a sinker bar 28. The sinker bar 28 extends transversely across the apparatus 10. A plurality of sinker fingers 30 extends forwardly from the sinker bar 28 in the machine direction 24. Each sinker finger 30 is spaced from a laterally adjacent finger 30 by a predetermined lateral spacing 32. The top surface of each sinker finger 30 is indicated by the character 30T, while the undersurface of each sinker finger 30 is indicated by the character 30S. The upper surface 20S of the platen 20 and the undersurface 30S of each sinker finger 30 cooperate to define a throat 34 into which the backing 14 is introduced into the apparatus 10.
A needle bar 40 having a plurality of penetrating needles 42 thereon is mounted beneath the platen 20. Each needle 42 may include a closure (not illustrated). The needle bar 40 is spaced a predetermined distance forwardly of the ends 30E of the sinker fingers 30. The needles 42 extend upwardly through the slots in the platen 20. The needle bar 40 is movable by a suitable actuator (not shown) such that the needles 42 are displaceable in vertically reciprocating fashion in a needle plane 44 located forwardly of the ends 30E of the sinker fingers 30 and normal to the path of travel. Each of the reciprocating needles 42 intersects and penetrates the backing 14 at a respective needle penetration point 46. Each needle penetration point 46 is located in the transverse spacing 32 defined between laterally adjacent sinker fingers 30. The transversely extending line of needle penetration points 46 lies in the needle plane 44.
A plurality of guide bars 50 is mounted above the sinker fingers 30 and above the planar path of travel of the backing 14 through the apparatus 10. Although a typical stitching apparatus may include up to four such guide bars, for clarity of illustration only the guide bars 50T, 50Y are illustrated in FIG. 1A. Each guide bar 50T, 50Y has a plurality of downwardly depending guide elements. The guide elements may be implemented as circular eyelets, as illustrated, or may take the form of tubular members or wide spoon guides, if desired.
The guide elements on the guide bar 50Y serve to carry the yarns 48Y that are laid into the top surface 14S of the backing 14. Each yarn 48Y is dispensed from a beam or from an individual bobbin mounted on a creel rack (not shown in FIG. 1A) and passes through a guide element on the yarn guide bar 50Y. The guide elements on the other guide bar 50T carry the stitching threads 48T that hold the yarns 48Y to the backing 14. Each stitching thread 48T is dispensed from a separate beam or from a bobbin mounted on a creel (not shown in FIG. 1A).
Each guide bar 550Y, 50T is independently movable in various degrees of freedom by a suitable actuating arrangement (not shown). Typically, each guide bar 50Y, 50T may be swung transversely, forwardly, and/or backwardly with respect to any other guide bar. Thus, the yarns 48Y and/or the threads 48T carried on the guide bars 50Y, 50T may be displaced with respect to the backing 14, and/or looped or interlocked with each other in a variety of fashions.
In operation, the backing 14 is introduced from the supply roll into the throat 34 defined between the platen 20 and the sinker fingers 30. The bottom surface 14B of the backing 14 is supported on the platen 20 while the top surface 14S is presented to the undersurface 30S of the sinker fingers 30. The dimension 34T of the throat 34 is larger than the thickness dimension 14T of the backing 14, so that the backing 14 is relatively loosely confined between the sinker fingers 30 and the platen 20 as the backing 14 is advanced along its path of travel through the apparatus 10.
Since the formation of laid-in yarn inlays 54 and the securement of those inlays 54 to the top surface 14S of the backing 14 by the underlaps 56U of the stitches 56 is sufficiently well understood, only a brief description of the process need be described.
The backing 14 is conveyed along the path of travel so that successive transversely extending regions of the backing 14 are advanced into the needle plane 44. Before and after the yarn guide bar 50Y is transversely displaced to dispense the length of yarn that eventually forms the inlay 54 on the surface 14S of the backing 14, stitching threads 48T from adjacent first and second thread guides on the thread guide bar 50T are successively looped around respective first and second locations on the dispensed length of yarn 48Y.
As successive transverse regions of the backing 14 move into the needle plane 44, adjacent first and second needles, e.g., the needles 42-1, 42-2, are actuated and raised through the backing at penetration points 46-1, 46-2, to positions above the path of travel. In the raised positions the adjacent first and second needles 42-1, 42-2 respectively successively engage the looped first and the second stitching threads 48T-1, 48T-2 and draw these stitching threads downwardly toward the backing 14. These actions draw the length of dispensed yarn 48Y to the surface 14S of the backing 14, thereby forming a yarn inlay 54 that extends transversely and diagonally over the first surface 14S of the backing 14. Continued downward movement of each needle 42-1, 42-2 through the backing 14 forms an underlap portion 56U of a chain stitch 56. The underlap portion 56U (FIG. 1B) of the stitch 56 overlies the first surface 14S of the backing 14 and secures the yarn inlay 54 against that first surface 14S. Each stitch 56 also includes an interlockable looped overlap portion 56L that lies against the bottom surface 14B of the backing 14. The arrangement of longitudinally extending overlap portions 56L of the chain stitches 56 on the bottom surface 14B of the backing 14 is best shown in the side elevational view of FIG. 1B.
For each successive longitudinal advance of a region of the backing 14 through the needle plane 44 each needle alternately cooperates with one of its laterally adjacent needles to form a yarn inlay element 54 that extends across the top surface 14S of the backing 14. As a result, as shown in the perspective view of FIG. 1A, the action of the thread guide bars 50T and the needles 42 forms a plurality of lines 58 of interlocked stitches 56, with each stitch 56 including an underlap portion 56U and an overlap portion 56L. Sequential overlap portions 56L interlock with each other, chain-fashion. The stitch lines 58 extend longitudinally in parallel along the backing 14. The frequency of stitches 56 is usually given in units of "courses", which indicate the number of stitches 56 per unit length of stitch line 58. Each stitch line 58 is spaced from an adjacent stitch line 58 by a predetermined stitch spacing, or "wale", W. The distance between longitudinally successive needle penetration points 46 in any given stitch line 58, termed the "stitch length", is indicated by the reference character "S".
Each yarn inlay 54 has a generally U-shaped configuration comprising a root portion 60 (FIG. 1C) with two branches 60B extending therefrom. The root portion 60 of the inlay 54 is held against the surface 14S of the backing 14 by the underlap portion 56U of a stitch 56. Each branch of a given yarn inlay 54 in one row is joined to a branch 60B of a yarn inlay 54 in an adjacent row to define a zig-zag array of inlays 54 on the top surface 14S of the backing 14. In the terminology of the art this arrangement of inlays 54 and stitching thread underlaps 56U may be identified as a reciprocating 0-0/2-2 stitch, or "tricot" stitch. "Laid Atlas" stitches such as 0-0/2-2/2-2/4-4 4-4/2-2/2-2/0-0, or longer laid stitches such as 0-0/3-3 or 0-0/4-4, may also be used.
As is seen in the front elevational view of FIG. 1C each yarn inlay 54 is substantially flat, that is, it lays directly against the first surface of the backing. The height of any vertical clearance, or gap (if one is present) between the yarn inlay 54 and the first surface 14 of the backing 12 is diagrammatically indicated in FIG. 1C by the reference character "h". In prior art laid-in stitch bonded structures the ratio h/W is substantially equal to zero. EQU --o--0--o--
In another well-known form of yarn structure 12' (FIG. 2A) the yarn 48Y is stitched into a backing 14 that is dimensionally stable in both its longitudinal and cross directions without the use of an overstitching thread. This form of stitched-in structure is typically used for towels, insulation structures, and wall coverings. FIG. 2A is a perspective view of an apparatus 10' used to produce this form of stitched-in yarn structure 12'. A commercially available apparatus similar in structure and operation to that described in connection with FIG. 2A is manufactured and sold under the Trademark "Malipol" by Karl Mayer Textilmaschinenfabrik GmbH, Obertshausen, Germany. Except for the distinctions to be noted the apparatus 10' is substantially identical to the prior art stitching apparatus 10 shown in FIG. 1A. Accordingly, identical reference characters are used for identical structural elements, while modified elements or modified structural relationships will be indicated by single primed reference characters.
One difference between the apparatus 10 of FIG. 1A and the apparatus 10' of FIG. 2A lies in the structure of the sinker fingers 30' and their disposition with respect to the needle penetration points 46. In the apparatus 10' the sinker fingers 30' extend forwardly (in the machine direction 24) beyond the needle penetration points 46. In addition, the portion of the fingers 30' forward of the needle penetration points 46 taper downwardly toward the backing 14. Since an overstitching thread 48T is not used since the apparatus 10' requires only the yarn guide bar 50Y.
In operation, a given yarn 48Y is engaged by adjacent needles 42 to form yarn elements 54' that are stitched-into the backing 14. A basic tricot stitch, such as a 1-0/1-2 stitch across two stitch rows, is typically formed. As the yarn 48Y is drawn by the needles toward the backing 14 the extension of the sinker finger 30' past the needle penetration points 46 prevents the yarn elements 54' from being drawn flat against the top surface 14T of the backing 14. Thus, each yarn element 54' exhibits an inverted loop portion 60L' that overlies the top surface 14S of the backing 14. As is illustrated in FIGS. 2A and 2B interlocking chain overlaps 56L' are formed adjacent the second (bottom) surface 14B of the backing 14. The loop portion 60L' of each yarn element 54' emanates from the needle penetration point 46, imparting a generally V-shaped configuration to the yarn element 54' in the vicinity of the surface 14S. Owing to the forward taper of the sinker fingers 30', as the backing 14 is advanced in the machine direction 24, the loop portions 60L' of the yarn elements 54' are easily doffed from the fingers.
The vertical clearance between the looped yarn element 54' and the top surface 14S of the backing 14 is again diagrammatically indicated in FIG. 2C by the reference character "h", while the spacing between adjacent longitudinally extending stitch lines 58' is again indicated by the reference character W. The apparatus 10' produces a pile structure 12' in which the ratio h/W of the loop height h to the stitch spacing W is substantially greater than zero. EQU --o--0--o--
Loop yarn structures 12" may also be formed using an array 16 of cross-laid weft-inserted yarns in lieu of a dimensionally stable backing. FIG. 3A illustrates a prior art apparatus 10" for forming this type of yarn structure 12". As is the case for the other illustrated prior art apparatus identical reference characters are used for identical structural elements, while modified structural elements or modified structural relationships will be distinguished by double primed reference characters.
Similar to the arrangement of FIG. 2A the apparatus 10" includes forwardly extending sinker fingers 30". The portion of the fingers 30" that extend forwardly past the needle penetration points 46 may have a substantially uniform height dimension 30H". As is the case for the arrangement of FIG. 1A the apparatus 10" includes both a yarn guide bar 50Y and a thread guide bar 50T.
The presence of the extending fingers 30" forms each yarn element 54" having an elevated pile loop 60L". As seen in FIGS. 3A and 3B the U-shaped root portion 60" of each yarn element 54" in each row of elements is secured to the weft yarns in the array 16 by an underlap 56U" of stitching thread. The point of contact between a weft yarn 16 and an underlap 56U" is indicated by the character 56M". The stitching threads 48T" are longitudinally interlocked by chained overlap portions 56L" that extend under the weft yarns 16. Adjacent stitch lines 58" are spaced transversely by the distance W. When only weft-inserted yarns are used the yarn elements 54" so formed tend to pull the stitching thread 48T and weft yarn 16, causing them to deflect upwardly in the lateral spacing 32" between the adjacent sinker fingers 30", as shown in FIG. 3C. Each loop portion 60L" of each yarn element 54" has a height dimension h, as measured from a reference plane P containing contact points 56M", thus imparting to the yarn structure 12" a h/W ratio greater than zero.
A commercially available apparatus similar in structure and operation to that described in connection with FIG. 3A is manufactured and sold under the Trademark "Schusspol" by Karl Mayer Textilmaschinenfabrik GmbH, Obertshausen, Germany. Variations of such apparatus utilizing pre-formed backings have also been suggested in German Democratic Republic Patent 244,582 (VEB Kombinat Textima). The difficulties in penetrating such backings with large amounts of binder to secure the pile loops onto the backing have culminated in using self-formed weft-inserted open backings as in the product produced by the apparatus of FIG. 3A, in preference to pre-formed, pre-stabilized backings. EQU --o--0--o--
Also known in the art are various knitting apparatus. One example of such apparatus is manufactured and sold under the Trademark "HKS 4-1" by Karl Mayer Textilmaschinenfabrik GmbH, Obertshausen, Germany. This apparatus is similar to that described in connection with FIG. 2A in that it has tapered sinker fingers that extend forwardly in the machine direction past the needle penetration points. However, in place of a backing that is dimensionally stable in both its length and width directions, the knitting apparatus also forms, in situ, a planar array of tricot stitch underlaps or weft-inserted yarns, similar to that shown in FIG. 3A. The pile yarns are usually knitted-in, with substantial amounts of yarn located below the planar array.
Products such as carpets, velours or velvets can be produced by similar machinery. These products require high stability against surface wear. Therefore, large amounts of binder material are applied from the backside of the structure to stabilize and reinforce the product. Representative of such knit pile structures are the commercial carpets manufactured using a "woven interlock construction" and sold by Mohawk Carpets, Inc., Calhoun, Ga.
FIG. 4 is a stylized front elevation view of a knit pile structure 12.sup.3 having yarn element 54.sup.3 with an elevated stitched-in pile loop 60L.sup.3. The root portion 60.sup.3 of each stitched-in pile yarn element 54.sup.3 is additionally secured by an underlap 56U.sup.3 of a stitch 56 to the weft yarns 16.sup.3 that form a backing 14.sup.3. The stitches 56 are longitudinally interlocked by chained overlap portions 56L.sup.3 that extend under the weft yarns 16.sup.3.
A longitudinally extending yarn 59 may be laid over the root portion 60.sup.3 of each yarn element 54.sup.3 in each stitch line 58.sup.3 and is there held by an underlap 56U.sup.3 of the stitch 56. A second longitudinally extending yarn 61 is laid under the weft yarn 16.sup.3 that and is there held by an overlap 56L.sup.3. The yarns 59 and 61 usually serve the purpose of filling or reinforcing the structure. In addition, a planar layer of weft-extending or laid-in yarns 62, 63 are held by the underlaps 56U.sup.3 and the overlap portions 56L.sup.3 of the stitches 56. These yarns 62, 63 also serve to reinforce the yarn structure 12.sup.3. EQU --o--0--o--
Each of the above-described known apparatus and processes have attendant disadvantages that are believed to detract from their utility in forming pile surface structures.
For example, the laid-in stitch-bonded structure produced by the apparatus of FIG. 1A is flat, has no pile height, and thus would be disadvantageous for use as a carpet because of the lack of cushion. Stabilization and reinforcement by applying binder from the back to qualify the product as a floor covering would penetrate into the entire length of the laid-in yarns and would stiffen the face yarns, rendering the surface of the product unattractive and harsh.
The apparatus of FIG. 2A is efficient and fast in operation, and the product produced is relatively easy to stabilize and reinforce by the addition of binder material to the back face to secure the overlaps of the pile yarns. Nevertheless, the pile yarn structure produced is believed to exhibit several disadvantages. The loops tend to lean forwardly because of the pull against the interlooped overlaps, and a very large amount of pile yarn is wasted under the backing in the form of chain stitch overlaps. Moreover, the taper of the sinker fingers downstream of the needle penetration plane causes the formed loops to be pulled and shortened, resulting in much lower loop height h as compared to the height of the sinker finger at the needle penetration plane. In addition, the pile loops 60L (FIG. 2C) emerge from a single, highly constricted, needle penetration opening in the backing, thus defining a "V-shape" rather than a "U-shape", thereby minimizing the coverage of the upper surface of the backing by the pile loop.
In the pile structure formed using the apparatus of FIG. 3A the weft-inserted yarns in the array tend to deflect upwardly between the two sinker elements, as shown in FIG. 3C. This has the effect of shortening the pile height. Furthermore, the stitching thread must pull and slide and fully surround two relatively loose yarns (pile and weft) and therefore it must be drawn very tightly. This slows down the process and limits the overall tightness that can be obtained. Moreover, the product is dimensionally unstable because of the absence of multidimensional ties in the backing layer, unless large amounts of adhesive binder are applied through all lower elements to stabilize the structure. Applying large amounts of binder from the back does not necessarily reach the roots of the U-shaped pile yarns to secure all filaments of the pile yarns. Relatively tight chain stitches exacerbate this problem since they tend to limit the propagation of liquid binder into the filaments of the pile yarn in the vicinity of the constricted roots. Converting the system of FIG. 3A into one utilizing a pre-formed stable backing has, to date, caused even more serious problems with sufficient binder penetration to the pile yarns through the backing, and also difficulties in obtaining sufficiently tight chain stitch overlaps to securely hold the pile yarns in place.
In the knit pile structure of FIG. 4 the pile emerges in a "V-shape" rather than a "U-shape", again minimizing the coverage of the upper surface of the backing. Relatively large amounts of pile yarn are consumed in forming the back face of the structure. Although the structure does allow the propagation liquid binder into the roots of the pile elements, relatively large amounts of binder are required to dimensionally stabilize the structure. EQU --o--0--o--
In view of the foregoing it is believed desirable to construct a pile surface structure over a prefabricated or in-situ-formed backing held under tight control, with all of the pile loop yarns located over the upper surface of the backing. It is also believed desirable to attach the pile elements to the backing with separate but tight underlaps of finer stitching thread, and to further secure the pile elements with binder primarily concentrated in the tightly constricted roots of the pile yarns. As a result a lightweight, stable and fully erect pile structure, providing maximum pile yarn coverage over the backing is produced.